[ccp4bb] anisotropic displacement parameter matrix shelxl

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CCP4bb <-- 1999 <-- November 1999 <-- 30 November 1999

Previous message:
Subject: twin?
From: Li Sheng sli {- at -} SIBS {- dot -} AC {- dot -} CN
Date: 2007-07-08

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Subject: Re: anisotropic displacement parameter matrix shelxl
From: Gerard Bricogne gb10 {- at -} GLOBALPHASING {- dot -} COM
Date: 2007-07-08

Subject: anisotropic displacement parameter matrix shelxl
From: artis {- at -} CHEMISTRY {- dot -} MONTANA {- dot -} EDU artis {- at -} CHEMISTRY {- dot -} MONTANA {- dot -} EDU
Date: 2007-07-08

Hello all,

I am trying to understand how the anisotropic displacement parameters
output by shelxl in the form U11 U22 U33 U23 U13 U12 relate with the
displacement in the x, y and z directions of say an ellipsoid in ORTEP.
So far I tried to find the eigenvalues for the matrix using the relationship

Ucart - (lambda)I
=0

where lambda would give the eigenvalues along the three principal axis. In
the above relationship, I assumed the

to stand for absolute value and
used just basic algebra to find the value of lambda, which will be the
inverse matrix for Ucart in this case. I used the reference

On the handling of atomic anisotropic displacement
parameters
R. W. Grosse-Kunstleve* and P. D. Adams
J. Appl. Cryst. (2002). 35, 477±480

to look up the above relationship. In the paper it is mentioned that

Ucart - (lambda)I
=0

is solved using Cardan's formula.

So I probably oversimplified my solution and have it wrong.

Can anyone please help me on this? Is there a simple way of knowing the
displacement along a major axis on the ellipsoid itself in terms of
Angstrom?
Thank you.

Arti S. Pandey
Chemistry and Biochemistry
Montana State University
Bozeman,MT 59717

CCP4bb navigation

CCP4bb <-- 1999 <-- November 1999 <-- 30 November 1999

Previous message:
Subject: twin?
From: Li Sheng sli {- at -} SIBS {- dot -} AC {- dot -} CN
Date: 2007-07-08

Next message:
Subject: Re: anisotropic displacement parameter matrix shelxl
From: Gerard Bricogne gb10 {- at -} GLOBALPHASING {- dot -} COM
Date: 2007-07-08